When an organic compound, especially a polymer or oligomer is used as an electronic device material, it is often used as thin films. Illustrative are insulating films, charge-transporting films, protecting films, and leveling films.
In organic electroluminescence (hereinafter abbreviated as “EL”) devices, charge-transporting thin films made of a polymer or oligomer or the like are used as hole transport layers (buffer layers) and/or charge injection layers (see, for example, Patent Document 1).
A charge-transporting thin film is required to be a uniform, roughness-free thin film. Roughness of a thin film induces the occurrence of dark spots and reductions in device characteristics due to short circuiting between an anode and a cathode. Such roughness, therefore, becomes a cause of a reduction in yield upon fabrication of organic EL devices. This roughness is considered to arise by coagulation of a material, and is considered to be attributable to a reduction in the uniformity of a thin film as a result of a localized rise or sink of the thin film.
Very small particles may also occur in a thin film in some instances. The occurrence of these particles is also considered to be attributable to the coagulation of its material. Those of this material as coagulated in the form of very fine particles are called “contamination particles”. The occurrence of contamination particles also gives devices such deleterious effects as mentioned above. The thickness of an organic layer in a general organic EL device is as small as from 200 to 1,000 nm, so that the existence of contamination articles becomes a direct cause of electric short circuiting between an anode and a cathode and is a serious problem for the device.
To solve the problem of contamination particles, it may be contemplated to replace a material, which is to be used, by another material. However, such a replacement is unable to obtain sufficient device characteristics in many instances, and requires numerous trials and errors for the selection of a material.
This problem of contamination particles is serious not only in thin films for electronic devices but also in other technical fields that use thin films.
For these reasons, there is an outstanding desire for the development of thin films free of contamination particles and also their fabrication method.
Patent Document 1:                Japanese Patent Laid-open No. 2002-151272        